1. Field of the Invention
The present invention relates to a fastening device that can be used in various machines, such as construction, electrical, or mechanical equipment, and that can be inserted and clamped by a one-touch operation.
2. Background of the Invention
Conventionally, there is a fastening device that can be inserted and clamped by one-touch operation; this is described in Japanese Examined Utility Model Publication No. S55-48171. FIGS. 25-27 illustrate this conventional fastening device 100, which comprises a base 110, running screws 120, 120, and a spring 130 consisting of a coil spring.
A bolt 140 is inserted into the base 110, and a bolt-insertion hole 150 is opened in the base 110. The bolt-insertion hole 150 that is formed in the base 110 has slope portions 160, 160. The radius of the lower parts of the slope portions 160, 160 of the bolt-insertion hole 150 is made smaller than the radius of the upper part of the slope portions 160, 160 of the bolt-insertion hole 150, and the running screws 120, 120 are supported on the slope portions 160, 160, respectively.
The running screws 120, 120 are opposed to each other in a pair, and female screws 121, 121 that are to be engaged with male screws 141, 141 of the bolts 140, 140 are formed in a longitudinal direction on the opposed faces of the running screws 120, 120. In addition, tapered faces 122, 122 that can freely slide on the above-mentioned slope portions 160, 160 are formed at the bottom of the running screws 120, 120.
A spring 130 is inserted into the base 110 in a manner so as to apply pressure to a pair of the opposed running screws 120, 120 from above. In order that the spring 130 can press the running screws 120, 120, a cover 170 is fixed on the top end of the base 110 by pressure fitting.
In such a structure, by mounting the cover 170 onto the base 110 with the spring 130 flexed to some degree, the running screws 120, 120 are pressed to move toward the bolt-insertion hole 150. As shown in FIG. 26, the bolt 140 is inserted in the base 110 from the bolt-insertion hole 150, so that the running screws 120, 120 slide upward on the slope portions 160, 160 against the spring force of the spring 130, and thus the bolt can be inserted between the running screws 120, 120. Then, the female screws 121, 121 of the running screws 120, 120 engage with the bolt 140 due to the spring force of the spring 130, and thus the bolt 140 can be fastened by a one-touch operation.
However, this conventional fastening device 100 has a shortcoming that the insertion of the bolt 140 can cause the running screws 120, 120 to become inclined or to slip down in the base 110. FIG. 27 shows such a situation where the running screws 120, 120 slip down. When the inserted bolt 140 pushes up the running screws 120, 120, the top portions of the running screws 120, 120 are inclined in a manner so as to approach or lean toward each other (as shown by the arrows), or to slip down. Such a displacement causes the bolt 140 to be hooked by the running screws 120, 120 when the bolt 140 is inserted, which hinders the bolt 140 from being inserted by a one-touch operation.
The present invention has been made in consideration of the above problems with a conventional fastening device, and one object of the present invention is to provide a fastening device that makes it possible to smoothly insert a bolt while preventing the inclination or slipping down of the running screws at the time that the bolt is inserted, and thereby makes it possible to perform fastening by a one-touch operation.